We propose to examine some medical and behavioral precursors of specific intellectual deficits in children born very prematurely and treated in a neonatal intensive care facility. A longitudinal study of survivors born in our hospital since 1969, with beirth weights less than 1500 g. will be continued for 3 more years to provide additonal data for 148 children born from 1972 to 1979. These data will nearly double the total assessments available at 6, 8, and 11 years of age, allowing for a more detailed analysis according to specific outcomes. Approximately 40 percent are expected to show impairment at 8 years severe enough to preclude normal school progress, ranging from degrees of mental retardation through significant learning and language disabilities. The sample is predominantly middle-class in origin, enhancing the significance of neonatal events for outcome. Analyses will examine: 1) the behavioral origins of specific handicaps at school age from data gathered across infancy and early childhood; 2) the significance to outcome of certain neonatal problems frequently associated with extreme prematurity, including specific physiological variables associated with asphyxia and apnea, nutrition, and fluid management. The cohort of preterm children will contain its own medical control group (normal vs. abnormal outcome); data from normal siblings will control for social/cultural effects. Our long range goal is to determine and thereby modify important predictors of childhood intellectual disabilities in this very high risk population.